As he mused on whether or not to marry, Charles Darwin drew up a list of pros and cons. One advantage, he noted in July 1838, was that his future wife would be an “object to be loved & played with — better than a dog anyhow”.

The pioneer of evolutionary theory, who also said that he believed that there were “differences in the mental powers of the sexes”, has never been noted for his feminist credentials, but a new study of his letters suggests that he was secretly progressive.

Philippa Hardman, a research associate at Cambridge University, found that Darwin